ryan's going to be with romney in virginia. the president is staying in colorado for a rally there. veronica? >> thank you. >>> nato forces in afghanistan say three international service members and their translator were killed in a suicide bombing in the eastern part of the country this morning. this as the war in afghanistan reached a grim milestone sunday with a death of the 2,000th u.s. service member. nbc's chief foreign correspondent richard engel has the details. >> reporter: there has been another insider attack, the so called green on blue attack, when afghan troops attack and kill their american partners. so far, this year, these kind of attacks have led to at least 20% of american combat deaths in afghanistan. a group of american soldiers were manning a check point, a vehicle control point, when they were approached by two afghan troops. the afghan soldiers walked up to the americans, they exchanged a few words with them. it's not exactly sure what was said between the american soldiers and the afghan soldiers. but then one of the afghan soldiers pulled out a weapon, open